Radio frequency-based particulate loading monitoring system

ABSTRACT

A particulate trap regeneration system is provided, which may include a particulate trap having a filter medium configured to remove one or more types of particulate matter from an exhaust flow of an engine and a regeneration device configured to reduce an amount of particulate matter in the particulate trap, as well as a radio frequency-based particulate loading monitoring system configured to determine an amount of particulate matter trapped by the filter medium. The particulate loading monitoring system may include at least one radio frequency transmitting probe configured to transmit radio frequency signals of predetermined magnitude and predetermined frequency toward the filter medium and at least one radio frequency receiving probe configured to receive and measure the magnitude of received radio frequency signals that pass through the filter medium. Further, the system may include a temperature sensing device configured to take a temperature measurement indicative of a temperature of the particulate trap at the time the radio signals are received by the receiving probe and a controller, which may be configured to determine, based on the measured magnitude of received radio frequency signals, a particulate loading value indicative of the amount of particulate matter trapped in the filter medium. The controller may also be configured to perform a temperature compensation including modifying, based on the temperature measurement, at least one of the following: the measured magnitude of the received radio frequency signals that pass through the filter medium or the particulate loading value.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11,189,530, filed Jul. 26, 2005, now U.S. Pat. No. 7,157,919the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure is directed to a particulate trap regenerationsystem and, more particularly, to a particulate trap regeneration systemhaving a particulate loading monitoring system.

BACKGROUND

Engines, including diesel engines, gasoline engines, natural gasengines, and other engines known in the art, may exhaust a complexmixture of air pollutants. The air pollutants may be composed of bothgaseous and solid material, such as, for example, particulate matter.Particulate matter may include ash and unburned carbon particles and maysometimes be referred to as soot.

Due to increased environmental concerns, exhaust emission standards havebecome more stringent. The amount of particulate matter and gaseouspollutants emitted from an engine may be regulated depending on thetype, size, and/or class of engine. In order to meet these emissionsstandards, engine manufacturers have pursued improvements in severaldifferent engine technologies, such as fuel injection, enginemanagement, and air induction, to name a few. In addition, enginemanufacturers have developed devices for treatment of engine exhaustafter it leaves the engine.

Engine manufacturers have employed exhaust treatment devices calledparticulate traps to remove the particulate matter from the exhaust flowof an engine. A particulate trap may include a filter designed to trapparticulate matter. The use of the particulate trap for extended periodsof time, however, may enable particulate matter to accumulate on thefilter, thereby causing damage to the filter and/or a decline in engineperformance.

One method of restoring the performance of a particulate trap mayinclude regeneration. Regeneration of a particulate trap filter systemmay be accomplished by thermal regeneration, which may includeincreasing the temperature of the filter and the trapped particulatematter above the combustion temperature of the particulate matter,thereby burning away the collected particulate matter and regeneratingthe filter system. This increase in temperature may be effectuated byvarious means. For example, some systems employ a heating element (e.g.,an electric heating element) to directly heat one or more portions ofthe particulate trap (e.g., the filter material or the externalhousing). Other systems have been configured to heat the exhaust gasesupstream from the particulate trap, allowing the flow of the heatedgases through the particulate trap to transfer heat to the particulatetrap. For example, some systems may alter one or more engine operatingparameters, such as air/fuel mixture, to produce exhaust gases with anelevated temperature. Running an engine with a “rich” air/fuel mixturecan elevate exhaust gas temperature. Other systems heat the exhaustgases upstream from the particulate trap, with the use of a burner thatcreates a flame within the exhaust conduit leading to the particulatetrap.

In some systems, regeneration may be performed continually. In othersystems, regeneration may be performed periodically. That is, after atrigger condition occurs, a thermal regeneration system may initiateregeneration in response to the trigger condition. Some systems areconfigured to initiate regeneration in response to a single type oftrigger condition, such as the operation of the engine for apredetermined amount of time or a pressure characteristic of the exhaustsystem (e.g., backpressure in the exhaust system). Some systems areconfigured to initiate regeneration in response to measurements of theamount of particulate matter accumulated in the particulate trap. Forexample, one such regeneration system is disclosed by U.S. Pat. No.4,477,771 issued to Nagy et al. on Oct. 16, 1984 (“the '771 patent”).The '771 patent discloses a regeneration system configured to initiateregeneration in response to a determination of power loss of microwavestransmitted through the filter medium within a particulate trap.

The system of the '771 patent may be configured to initiate regenerationin response to a determination of power loss of a radio frequency (RF)signal. However, the system of the '771 patent utilizes microwavesrather than low frequency RF signals. For example, the '771 patentdiscloses use of RF signals having frequencies on the order of 1.85 GHz(1850 MHz). Use of higher frequencies, such as the microwaves used inthe '771 patent, requires system components that are more complicatedand thus cost more at each stage of development and production. Further,the use of microwaves, as in the '771 patent, often requires a waveguideor resonant chamber. The requirement of such a chamber may limit thedesign possibilities of a particulate trap housing.

The present disclosure is directed to solving one or more of theproblems described above.

SUMMARY OF THE INVENTION

In one aspect, the present disclosure is directed to a particulate trapregeneration system. The system may include a particulate trap having afilter medium configured to remove one or more types of particulatematter from an exhaust flow of an engine and a regeneration deviceconfigured to reduce an amount of particulate matter in the particulatetrap. The system may also include a radio frequency-based particulateloading monitoring system configured to determine an amount ofparticulate matter trapped by the filter medium. The particulate loadingmonitoring system may include at least one radio frequency transmittingprobe configured to transmit radio frequency signals of predeterminedmagnitude and predetermined frequency toward the filter medium. Theparticulate loading monitoring system may also include at least oneradio frequency receiving probe configured to receive and measure themagnitude of received radio frequency signals that pass through thefilter medium. Further, the particulate loading monitoring system mayinclude a temperature sensing device configured to take a temperaturemeasurement indicative of a temperature of the particulate trap at thetime the radio signals are received by the receiving probe. In addition,the particulate loading monitoring system may include a controller,which may be configured to determine, based on the measured magnitude ofreceived radio frequency signals, a particulate loading value indicativeof the amount of particulate matter trapped in the filter medium. Thecontroller may also be configured to perform a temperature compensationincluding modifying, based on the temperature measurement, at least oneof the following: the measured magnitude of the received radio frequencysignals that pass through the filter medium or the particulate loadingvalue. The particulate trap regeneration system may also be configuredto activate the regeneration device in response to the particulateloading monitoring system detecting more than a predetermined amount ofparticulate matter trapped in the filter medium.

In another aspect, the present disclosure is directed to a method ofregenerating a particulate trap. The method may include determining anamount of particulate matter trapped by a filter medium of a particulatetrap configured to remove one or more types of particulate matter froman exhaust flow of an engine. The method may include transmitting radiofrequency signals of predetermined magnitude and predetermined frequencytoward a filter medium and receiving and measuring the magnitude ofreceived radio frequency signals that pass through the filter medium.The method may also include taking a temperature measurement indicativeof a temperature of the particulate trap at the time the radio signalsare received. Further, the method may include determining, based on themeasured magnitude of received radio frequency signals, a particulateloading value indicative of the amount of particulate matter trapped inthe filter medium. In addition, the method may include performing atemperature compensation including modifying, based on the temperaturemeasurement, at least one of the following: the measured magnitude ofthe received radio frequency signals that pass through the filter mediumor the particulate loading value. The method may also include activatinga regeneration device, configured to reduce an amount of particulatematter in the particulate trap, in response to the particulate loadingmonitoring system detecting more than a predetermined amount ofparticulate matter trapped in the filter medium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of a machine according to anexemplary disclosed embodiment.

FIG. 2 is a diagrammatic illustration of a particulate trap regenerationsystem according to an exemplary disclosed embodiment.

FIG. 3 is a schematic of a particulate loading monitoring systemaccording to an exemplary disclosed embodiment.

FIG. 4 is a schematic of a narrowband particulate loading monitoringsystem according to an exemplary disclosed embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to the drawings. Wherever possible,the same reference numbers will be used throughout the drawings to referto the same or like parts.

FIG. 1 illustrates a machine 10. Machine 10 may include an operatorstation 11, one or more traction devices 12, a frame 13, an engine 14,which may be mounted to frame 13, and a particulate trap regenerationsystem 16.

Although machine 10 is shown as a truck, machine 10 could be any type ofmachine having an exhaust producing engine. Accordingly, tractiondevices 12 may be any type of traction devices, such as, for example,wheels, as shown in FIG. 1, tracks, belts, or any combinations thereof.

Engine 14 may be any kind of engine that produces an exhaust flow ofexhaust gases. For example, engine 14 may be an internal combustionengine, such as a gasoline engine, a diesel engine, a gaseous fuelburning engine or any other exhaust gas, producing engine.

System 16 may include an after-treatment device 18. After-treatmentdevice 18 may be any type of device configured to remove one or moreconstituents from the exhaust flow of engine 14. In some embodiments,after-treatment device 18 may be regenerated by heat or some othermeasure. In one embodiment, after-treatment device 18 may include aparticulate trap 19. Particulate trap 19 may be configured to remove oneor more types of particulate matter from the exhaust gases produced byengine 14 and flowing through an exhaust conduit 20 configured to directall or a portion of the exhaust gases produced by engine 14 toafter-treatment device 18. Particulate trap 19 may include an outerhousing 22, which may encase a filter medium 24 (e.g. a metal mesh orscreen, or a porous ceramic material, such as cordierite) configured toremove (i.e., trap) one or more types of particulate matter from theexhaust flow of engine 14.

Although after-treatment device 18 is discussed herein primarily asbeing a particulate trap, in other embodiments, after-treatment device18 may include multifunctional devices such as a combination of acatalytic converter and a particulate trap in the same unit or acatalytic particulate trap, wherein filter medium 24 may include acatalytic material and/or a catalytic coating.

After-treatment device 18 may be configured to be thermally regenerated.That is, regeneration of after-treatment device 18 may be accomplishedby increasing the temperature of after-treatment device 18. Suchincreases in temperature of after-treatment device 18 may be generatedin a number of different ways. For example, heat may be directly appliedto after-treatment device 18 via a heating device integral with oradjacent to after-treatment device 18. An example of such a heatingdevice may include an electric heating element (not shown).

Alternatively or additionally, the temperature of after-treatment device18 may be increased by heat transferred to it from the exhaust gasesflowing through it. In such embodiments, heat may be applied to exhaustgases upstream from after-treatment device 18. The temperature of theexhaust gases may be increased in one or more ways. For example,altering engine parameters may have an effect on exhaust gastemperature. Running engine 14 with a “rich” air/fuel mixture mayincrease exhaust gas temperature. Increases in engine load may alsoincrease exhaust gas temperature. Exhaust gases may also be heated bypost injection, which involves injecting additional fuel into thecombustion chambers after the combustion has taken place, which mayresult in the additional fuel being burned in the exhaust system,thereby elevating the temperature of the exhaust gases in the system.

Exhaust temperature may also be raised by heating the exhaust gases orexhaust conduit 20. For example, an electric heating element and/orflame producing burner may be configured to heat the exhaust gases orexhaust conduit 20. In one embodiment, system 16 may include aregeneration device 25 configured to reduce an amount of particulatematter in after-treatment device 18. For example, regeneration device 25may include a burner assembly 26 configured to increase the temperatureof the exhaust gases flowing through exhaust conduit 20 upstream fromafter-treatment device 18. Burner assembly 26 may be configured tomaintain or restore the performance of after-treatment device 18 throughthermal regeneration. Accumulation of exhaust flow constituents inafter-treatment device 18 may result in a decline in engine performanceand/or possible damage to after-treatment device 18 and/or othercomponents of system 16.

Burner assembly 26 may be configured to prevent or restore any declinein engine performance and avoid possible damage to after-treatmentdevice 18 and/or other components of system 16. For example, burnerassembly 26 may be configured to cause at least some of the particulatematter that may have accumulated in after-treatment device 18 to beburned off.

Although system 16 is shown with a single after-treatment device 18 anda single regeneration device 25, system 16 may include more than oneafter-treatment device 18 and/or more than one regeneration device 25.For example, in one embodiment, system 16 may include a singleregeneration device 25 configured to regenerate two after-treatmentdevices. In another embodiment, system 16 may include two regenerationdevices configured to regenerate two after-treatment devices. In such anembodiment, each regeneration device may be configured to regenerate oneof the after-treatment devices or contribute to the regeneration of bothof the after-treatment devices. System 16 could also include any numberof regeneration devices and/or after-treatment devices in anycombination suitable for regeneration.

FIG. 2 illustrates an exemplary embodiment of particulate trapregeneration system 16. For purposes of the following explanation,after-treatment device 18 will be discussed as being particulate trap19, while regeneration device 25 will be discussed as being burnerassembly 26. However, it should be noted that after-treatment device 18and regeneration device 25 could be any of the disclosed types ofafter-treatment and regeneration devices mentioned above. System 16 mayalso include a controller 28 configured to receive information fromvarious sources and control one or more components of system 16 based onthis information.

Burner assembly 26 may be positioned anywhere along exhaust conduit 20between engine 14 and particulate trap 19. Burner assembly 26 mayinclude a fuel injector 30 configured to supply fuel to burner assembly26. Burner assembly 26 may be configured to create a flame, which may bein a heat exchange relationship with the exhaust flow. System 16 may beconfigured to supply fuel injector 30 with fresh air for mixing with thefuel for combustion, as well as for flushing fuel injector 30 of anyfuel or debris before and/or after operation of burner assembly 26. Thesupply of air to fuel injector 30 may be regulated by an air valve 31,controllable by controller 28.

In some embodiments, the source of the fresh air may be an air intakesystem 32 of engine 14. That is, air may be routed from a portion of airintake system 32, such as an intake manifold 34, downstream from acompressor 36 configured to create forced induction for engine 14.Compressor 36 may include a turbocharger, supercharger, or any otherdevice configured to compress intake air and thereby produce forcedinduction for engine 14. Air may be directed from intake manifold 34 tofuel injector 30 via an air conduit 38. The supply of air to fuelinjector 30 may be regulated by air valve 31, which may be controllableby controller 28 as discussed above.

Burner assembly 26 may also include a spark plug 40 configured toprovide spark to ignite the air/fuel mixture delivered by fuel injector30. Current may be supplied to spark plug 40 by an ignition coil 42,which may be controllable by controller 28. Although burner assembly 26has been shown and described as including spark plug 40, alternativeignition sources may be employed, such as, for example, glow plugs orany other means for igniting an air/fuel mixture.

System 16 may also include a radio frequency-based particulate loadingmonitoring system 44 configured to determine an amount of particulatematter trapped by filter medium 24. Each component of particulateloading monitoring system 44 may be located or configured to be locatedon board machine 10.

Particulate loading monitoring system 44 may include a radio frequencysynthesizer 46 configured to deliver radio frequency signals to a radiofrequency transmitting probe 48, which may be configured to transmit theradio frequency signals to thereby introduce them to filter medium 24.Particulate loading monitoring system 44 may also include a radiofrequency receiving probe 50 configured to receive radio frequencysignals that pass through filter medium 24.

Radio frequency transmitting probe 48 and receiving probe 50 may be anyof a number of shapes and sizes and may be situated in and/or aroundfilter medium 24 in various ways. The shape and configuration oftransmitting probe 48, receiving probe 50, after-treatment device 18,and filter medium 24 may influence the transmission of radio frequencysignals through filter medium 24, as well as detection of suchtransmission. As such, these components may be designed to optimizetransmission and reception of a selected frequency or frequency rangewithin one or more filter system geometries.

In addition, particulate loading monitoring system 44 may be furtherconfigured to detect magnitudes of radio frequency signals reflected byradio frequency transmitting probe 48 and determine the amount ofparticulate matter trapped by the filter medium 24 based on the detectedmagnitudes of radio frequency signals reflected by transmitting probe48. As more particulate matter accumulates on filter medium 24, thepermittivity of filter medium 24 changes. Due to this change inpermittivity, the magnitude of RF signal reflected by transmitting probe48 changes. Therefore, in a calibrated system, detected, reflected RFsignals can be used to determine the amount of particulate matteraccumulated on filter medium 24. A measurement of reflected RF signalmay be used by itself or in conjunction with a measurement of signalloss across filter medium 24 to determine the amount of particulatematter accumulated in filter medium 24.

In some embodiments, particulate loading monitoring system 44 may beconfigured to transmit a frequency swept signal, i.e., signals ofvarying frequency within a predetermined band of frequencies. Forexample, particulate loading monitoring system 44 may be configured totransmit signals of a predetermined magnitude and having frequenciesless than about 500 MHz. In certain embodiments, the frequency sweptsignal may include a band of frequencies between about 100-400 MHz.

Particulate loading monitoring system 44 may be configured to determineRF signal loss across filter medium 24. That is, particulate loadingmonitoring system 44 may be configured to measure the magnitude of thereceived radio frequency signals that pass through filter medium 24 andcompare the measured magnitude of the received signals of one or morefrequencies to the magnitude of the transmitted signals of the same oneor more frequencies.

For example, particulate loading monitoring system 44 may be configuredto compare the magnitude of signal of each frequency transmitted to themagnitude of signal of the same frequency that is received. Thedifference between these two magnitudes is the signal loss at thatfrequency, the value of which may be measured in dB or dBm. Particulateloading monitoring system 44 may be configured to make thisdetermination for each frequency at which a signal is transmitted bytransmitting probe 48.

Controller 28 may be configured to determine the amount of particulateloading in particulate trap 19 based on the signal loss value.Alternatively or additionally, controller 28 may be calibrated toconvert the measured magnitude of received and/or reflected radiofrequency signals directly to a particulate loading value.

Controller 28 may include any means for receiving machine operatingparameter-related information and/or for monitoring, recording, storing,indexing, processing, and/or communicating such information. These meansmay include components such as, for example, a memory, one or more datastorage devices, a central processing unit, or any other components thatmay be used to run an application.

Although aspects of the present disclosure may be described generally asbeing stored in memory, one skilled in the art will appreciate thatthese aspects can be stored on or read from types of computer programproducts or computer-readable media, such as computer chips andsecondary storage devices, including hard disks, floppy disks, opticalmedia, CD-ROM, or other forms of RAM or ROM. Various other knowncircuits may be associated with controller 28, such as power supplycircuitry, signal-conditioning circuitry, solenoid driver circuitry,communication circuitry, and other appropriate circuitry.

Controller 28 may perform multiple processing and controlling functions,such as, for example, engine management (e.g., controller 28 may includean engine control module, a.k.a. an ECM), monitoring of particulateloading, and controlling regeneration of particulate trap 19.Alternatively, machine 10 may include multiple controllers (aconfiguration shown in FIGS. 3 and 4), each dedicated to perform one ormore of these or other functions. Such multiple controllers may beconfigured to communicate with one another. For example, particulateloading monitoring system 44 may include a first controller/processor,which may be configured to determine the amount of particulate matteraccumulated in filter medium 24 based on the signals transmitted bytransmitting probe 48 and those detected by receiving probe 50, as wellas detected power reflected by transmitting probe 48. Such a dedicatedcontroller may also be configured to forward this determination ofparticulate accumulation to a second controller/processor, which may beconfigured to control regeneration in response to such information fromthe first controller.

Controller 28 may be configured to receive the signals detected byreceiving probe 50 or information about such signals. Controller 28 maybe further configured to activate regeneration device 25 in response toparticulate loading monitoring system 44 detecting more than apredetermined amount of particulate matter trapped in filter medium 24.

Controller 28 may also be configured to activate regeneration device 25in response to one or more other trigger conditions. These other triggerconditions may include, for example, operation of engine 14 for apredetermined amount of time; consumption of a predetermined amount offuel by engine 14; detection of an elevated backpressure upstream ofparticulate trap 19 above a predetermined pressure; detection of apressure differential across particulate trap 19 of greater than apredetermined amount; and a determination that a calculated amount ofparticulate matter accumulated in particulate trap 19 is above apredetermined amount.

Regeneration may also be initiated manually by an operator, owner,service technician, etc. of machine 10. Manually triggering regenerationmay be accomplished via a switch, button, or the like associated withmachine 10 and/or a service tool configured to interface with machine10.

System 16 may include various sensors configured to generate informationabout operating parameters of system 16. Such information may bereceived by controller 28. For example, system 16 may include anupstream temperature sensor 52, an upstream pressure sensor 54, adownstream temperature sensor 56, and a downstream pressure sensor 58.Such sensors may be positioned along exhaust conduit 20 upstream anddownstream from particulate trap 19 respectively and configured to takemeasurements of the temperature and pressure of the exhaust gases withinexhaust conduit 20 at their respective locations. Such measurements maybe received by controller 28.

Upstream pressure sensor 54 and downstream pressure sensor 58 mayconstitute a pressure differential measurement system. Such a system maybe configured to measure a pressure differential between an upstreampressure of the exhaust flow upstream from particulate trap 19 and adownstream pressure of the exhaust flow downstream from particulate trap19. Alternatively, in lieu of upstream pressure sensor 54 and downstreampressure sensor 58, the pressure differential measurement system mayinclude a single pressure differential sensor (not shown) configured tomeasure the difference in pressure between the exhaust flow upstream anddownstream of particulate trap 19.

System 16 may also include a ground speed sensor 60 configured tomonitor the ground speed of machine 10 (i.e., the speed of machine 10relative to the surface over which it travels). System 16 may also beprovided with a flame sensing system associated with burner assembly 26and configured to detect whether burner assembly 26 is currentlyproducing a flame. Such a flame sensing system may include, for example,a flame sensor 62. In addition, system 16 may include an engine speedsensor 64 configured to measure the speed at which engine 14 isoperating (i.e., rpm).

The aforementioned sensors may include any type of sensing meanssuitable for monitoring their respective parameters. In particular,flame sensor 62 may include any type of sensor suitable for detectingthe presence of a flame, such as temperature sensors (e.g.,thermocouples), optical sensors, ultraviolet sensors, and ion sensors.Flame sensor 62 may be configured to detect a condition (e.g.,temperature, ultraviolet light, ions, etc.) in proximity to the flame.Such a condition may be monitored at any location within close enoughproximity to the flame to enable the presence of the flame to bedetected. Additionally or alternatively, the flame sensing system may beconfigured to detect a rate of change in the condition. For example, atemperature in proximity to the flame location that is increasing at apredetermined rate may indicate that a flame is lit and causing theincrease

In addition or as an alternative to flame sensor 62, upstreamtemperature sensor 52 may be located upstream of burner assembly 26. Insuch an embodiment the flame sensing system may be configured todetermine whether the downstream exhaust temperature measured bydownstream temperature sensor 56 exceeds the upstream exhausttemperature measured by upstream temperature sensor 52 by apredetermined amount. A significantly higher downstream temperature mayindicate that the flame is lit and is thus heating exhaust gases as theyflow through burner assembly 26.

In some embodiments, upstream temperature sensor 52 or any othertemperature sensing device may be configured to take a temperaturemeasurement indicative of a temperature of particulate trap 19. Suchtemperature measurements may be taken in a manner suitable fordetermining the temperature of particulate trap 19 at the time the radiosignals are received by receiving probe 50. Controller 28 may beconfigured to determine, based on the measured magnitude of radiofrequency signals received by receiving probe 50, a particulate loadingvalue indicative of the amount of particulate matter trapped in filtermedium 24. Controller 28 may also be configured to perform a temperaturecompensation, which may include modifying, based on the temperaturemeasurement, at least one of the following: the measured magnitude ofthe received radio frequency signals that pass through the filter mediumor the particulate loading value. In embodiments configured to determinea signal loss value, the signal loss value may be modified to facilitatethe temperature compensation.

The temperature compensation may involve a function that is based on thetemperature measurement and at least one of the following: the measuredmagnitude of the received radio frequency signals that pass throughfilter medium 24 or the particulate loading value. In some embodimentsthe function may be based on a signal loss value. Further, in someembodiments, the function may be a third order polynomial. That is, thedetermination of actual particulate loading may be a function of thetemperature measurement and observed particulate loading, which may berepresented by the measured magnitude of the received radio frequencysignals that pass through filter medium 24, the signal loss value,and/or the particulate loading value. Alternatively, the temperaturecompensation may involve a look-up table based on the temperaturemeasurement and observed particulate loading, as represented by theaforementioned values.

Controller 28 may include a timing device 66. Controller 28 may beconfigured to couple information from timing device 66 with informationfrom other sources. For example, controller 28 may utilize informationfrom timing device 66 in conjunction with information regardingoperation of engine 14 (e.g., from engine speed sensor 64 to determinehow long engine 14 is operated. Timing device 66 may also be used tomonitor and control duration of regeneration events or any otheroperating parameters of system 16 and/or machine 10.

System 16 may be configured to control one or more additional systemfunctions and/or parameters. Controller 28 may be configured to controlthe pressure of the fuel delivered to fuel injector 30 (and thereforethe rate of fuel injection). A fuel on/off valve 68, which may becontrollable by controller 28, may be associated with fuel injector 30to selectively allow fuel to be delivered to fuel injector 30. Inaddition to fuel on/off valve 68, system 16 may also include a fuelpressure regulator valve 70 controllable by controller 28 to regulatethe pressure of the fuel, and thereby the rate at which fuel isdelivered to fuel injector 30. In some embodiments, controller 28 may beconfigured to control the pressure of fuel delivered to fuel injector 30in a closed loop fashion, i.e., in response to pressure measurementstaken at or near fuel injector 30 (e.g., by a fuel pressure sensor, notshown).

Controller 28 may be further configured to control fuel on/off valve 68and/or fuel pressure regulator valve 70 (i.e., flow of fuel to fuelinjector 30) in response to other parameters of system 16. For example,controller 28 may be configured to control the temperature of exhaustgases entering particulate trap 19 in response to feedback from upstreamtemperature sensor 52. This upstream exhaust temperature may becontrolled by regulating the amount of fuel and/or air supplied to fuelinjector 30, which may be accomplished by controlling fuel on/off valve68 and/or fuel pressure regulator valve 70. Other types of regenerationdevices or methods may be controlled in response to measurements takenby upstream temperature sensor 52. For example, the amount of postinjection may be varied (e.g., by controller 28) to control thetemperature of the exhaust gases entering any kind of after-treatmentdevice 18.

System 16 may include multiple fuel pressure regulator valves, which maybe independently controlled. At least one fuel pressure regulator valve70 may be configured to regulate main fuel pressure, and a second fuelpressure regulator valve (not shown) may be configured to regulate pilotfuel pressure. Pilot fuel pressure may be used during a pilot mode inwhich system 16 utilizes a predetermined air/fuel mixture to preventflameouts during various engine operating conditions, e.g., hardaccelerations and rapid decelerations.

Other operating parameters of system 16 may be monitored to maintainand/or optimize control of the regeneration process. For example,downstream temperature sensor 56 may detect whether downstream exhausttemperature is above a predetermined temperature. If downstream exhausttemperatures get too high, it could be an indication that temperatureswithin particulate trap 19 may be at an undesirably high level as welland/or that the regeneration may be somewhat unstable (e.g.,incineration of particulate matter and/or a catalyst driven reaction maybe intensifying within after-treatment device 18 beyond a levelcommanded by controller 28).

System 16 may also be configured to monitor the stability of theregeneration process by determining a difference between the upstreamexhaust temperature measured by upstream temperature sensor 52 and thedownstream exhaust temperature measured by downstream temperature sensor56. If the temperature measured by downstream temperature sensor 56exceeds that measured by upstream temperature sensor 52 by more than apredetermined amount for more than a predetermined amount of time,controller 28 may initiate steps to scale back or terminate theregeneration process. For example, in such a case, controller 28 mayreduce the intensity of the flame produced by burner assembly 26. Insome circumstances, controller 28 may terminate the regeneration processif the regeneration process is significantly unstable. For example, ifthe downstream exhaust temperature exceeds a predetermined value or itexceeds the upstream exhaust temperature by more than a predeterminedamount, then controller 28 may terminate the regeneration process.

Controller 28 may be configured to log faults when the downstreamexhaust temperature exceeds a predetermined temperature or when thedownstream exhaust temperature exceeds the upstream exhaust temperatureby more than a predetermined amount. Controller 28 may also beconfigured to terminate the regeneration process if the number of faultsreaches a predetermined value (e.g., when three faults have occurred).

System 16 may include a display 72. Display 72 may be located at anysuitable location on machine 10, such as, for example, in operatorstation 11. Display 72 may be any kind of display, including screendisplays, such as, for example, cathode ray tubes (CRTs), liquid crystaldisplays (LCDs), plasma screens, and the like. Display 72 may beconfigured to display information about operating parameters of system16. In one embodiment, display 72 may include a warning indicator 74(e.g., a warning lamp, warning message, etc.). Controller 28 may beconfigured to illuminate warning indicator 74 upon detection of thepredetermined amount of faults. As an alternative or in addition todisplay 72, system 16 may include one or more audible alerts forconveying information about operating parameters of system 16 to anoperator. In addition to providing visual feedback regarding operatingparameters of system 16, display 72 may also be configured to displayother information regarding system 16 or any other device and/or systemassociated with machine 10. Display 72 may also be configured toindicate when a regeneration event is occurring or about to occur.Alternatively or additionally, display 72 may be configured to displayinformation regarding particulate loading monitoring system 44.

FIG. 3 illustrates an exemplary schematic of particulate loadingmonitoring system 44. Particulate loading monitoring system 44 mayinclude a controller unit 76, which may include multiple components,such as an A/D converter 78 and a synthesizer interface 80. In someembodiments, the functions and components of controller unit 76 may beincorporated into controller 28. In other embodiments, controller unit76 may be separate from controller 28. In such embodiments, controllerunit 76 may include a Controller Area Network (CAN) interface 82configured to enable communication with one or more other components,such as controller 28, via a CAN datalink or any other suitable datalinkor communication format.

Synthesizer interface 80 may be configured to enable communication withand thereby control of frequency synthesizer 46. Synthesizer 46 may beconfigured to deliver RF signals to particulate trap 19, as discussedabove, along an interconnect 86, such as a wire, cable, etc. Particulateloading monitoring system 44 may include a directional coupler 88configured to monitor RF signals traveling in both directions alonginterconnect 86. As such, directional coupler 88 may be configured tomeasure the amount of RF power delivered to transmitting probe 48(“Forward Power” 90). Particulate loading monitoring system 44 may befurther configured to relay this measurement of forward power back tocontroller unit 76. Directional coupler 88 may also be configured tomeasure the amount of RF power reflected by transmitting probe 48(“Reflected Power” 92). Particulate loading monitoring system 44 may befurther configured to relay this measurement of reflected power back tocontroller unit 76. Particulate loading monitoring system 44 may also beconfigured to measure the amount of RF power received by receiving probe50 (“Received Power” 94) and relay this measurement back to controllerunit 76. From these measurements of forward power and received power,controller unit 76 may determine the amount of power loss (i.e., RFsignal loss) across filter medium 24 of particulate trap 19.

Other aspects of system 16 may also be measured, such as upstreampressure (96), downstream pressure (98), upstream temperature (100), anddownstream temperature (102). These and/or other measurements may alsobe forwarded to controller unit 76 to provide further information fromwhich to assess the amount of particulate matter accumulated inparticulate trap 19.

Particulate loading monitoring system 44 may include other signalprocessing components, as shown in an exemplary fashion in FIG. 3. Forexample, particulate loading monitoring system 44 may include a bandpassfilter 104, one or more attenuators 106, one or more short circuitprotection devices 108, one or more amplifiers 109, and/or one or morelog amps 110.

In some embodiments, particulate loading monitoring system 44 may befurther configured to filter out all received RF signals except forsignals within a predetermined band of frequencies that correspond withthe frequencies of the signals transmitted by transmitting probe 48.FIG. 4 illustrates an exemplary schematic of a narrowband particulateloading monitoring system 112. Filtering of the received RF signals mayprevent interference from other RF signals from external sources thatmay be detected by receiving probe 50 but fall outside the predeterminedrange of frequencies within which particulate loading monitoring system44 is designed to operate.

Narrowband system 112 may include many or all of the components ofparticulate loading monitoring system 44 shown in FIG. 3, and mayfurther include additional signal processing and/or filteringcomponents. For example, narrowband system 112 may include one or moretunable bandpass filters 114, one or more frequency mixers 116, one ormore narrow bandpass filters 118, and an injection oscillator 120.

Tunable bandpass filters 114 may be employed to filter out at least aportion of received RF signals that are outside of the desired frequencyband. Frequency mixers 116 may be employed to convert a frequency sweptRF signal to a single frequency, e.g., 10.7 MHz. Such conversion mayfacilitate further signal processing. Narrow bandpass filters 118 may beemployed to filter out signals that are not within a small margin oferror from the single frequency, for example, within 100-200 KHz of 10.7MHz.

Narrowband system 112 may include a tracking signal generator 122. Insuch narrowband embodiments, synthesizer 46 may produce an offsetfrequency from that to be transmitted by transmitting probe 48. Theoffset signal may be directed to frequency mixers 116 for conversion ofthe received signal and the reflected signal. Injection oscillator 120may be employed to convert the offset signal to the desired signalbefore being delivered to transmitting probe 48. To make such aconversion, injection oscillator 120 may include an oscillator 124(e.g., 10.7 MHz), a bandpass filter 126, and a frequency mixer 128. Theoffset signal may be mixed with signal from oscillator 124 to produce atracking signal to be applied to transmitting probe 48. Narrowbandsystem 112 may also include various other signal processing devices,such as bandpass filters 104, attenuators 106, amplifiers 109, log amps110, etc.

INDUSTRIAL APPLICABILITY

The disclosed particulate trap regeneration system 16 may be suitable toenhance exhaust emissions control for engines. System 16 may be used forany application of an engine. Such applications may include, forexample, stationary equipment such as power generation sets, or mobileequipment, such as vehicles. The disclosed system may be used for anykind of vehicle, such as, for example, automobiles, machines (includingthose for on-road, as well as off-road use), and other heavy equipment.

The presently disclosed system may be mounted on board any type ofstationary or mobile equipment. In order for the components of thedisclosed system to be sized appropriately for on board incorporation,the system may be configured to generate and measure RF signals only inthe specific range of frequencies with which the system is designed tooperate, rather than being configured to generate a much wider range offrequencies. By focusing the capabilities of the system components insuch a manner, the size of one or more system components may be scaleddown. Focused capabilities and smaller size of system components maymake particulate loading monitoring by an RF measurement techniquepractical in terms of cost and size.

An exemplary method of regenerating particulate trap 19 may includedetermining an amount of particulate matter trapped in filter medium 24of particulate trap 19. Such a determination may be accomplished bytransmitting radio frequency signals of predetermined magnitude andpredetermined frequency toward filter medium 24 and receiving andmeasuring the magnitude of received radio frequency signals that passthrough filter medium 24. The method may also include taking atemperature measurement indicative of a temperature of particulate trap19 at the time the radio signals are received and determining, based onthe measured magnitude of received radio frequency signals, aparticulate loading value indicative of the amount of particulate mattertrapped in filter medium 24.

The method may also involve performing a temperature compensationincluding modifying, based on the temperature measurement, at least oneof the following: the measured magnitude of the received radio frequencysignals that pass through filter medium 24 or the particulate loadingvalue. The temperature compensation may involve a function based on thetemperature measurement and at least one of the following: the measuredmagnitude of the received radio frequency signals that pass through thefilter medium or the particulate loading value. An example of such afunction may be a third order polynomial. Alternatively, the temperaturecompensation may include referring to a look-up table based on thetemperature measurement and at least one of the following: the measuredmagnitude of the received radio frequency signals that pass through thefilter medium or the particulate loading value.

The radio frequency signals that are transmitted toward filter medium 24may have frequencies of less than about 500 MHz. An exemplary band offrequencies that may be transmitted may be about 100-400 MHz. Inchoosing the range of radio frequencies to be used herein, a number ofconsiderations may be evaluated. For example, the amount of transmissionloss over the selected frequency range should provide for, among otherthings, suitable measurement sensitivity (i.e., attenuation per unit ofparticulate matter present) and a more linear response as a function ofradio frequency signal attenuation than is possible at a singlefrequency. The selected range of frequencies should also avoid problemsassociated with power source frequency drift with time. Further,averaging reduces the effects of temperature on accumulated particulatematter and filter permittivity, which would otherwise requiretemperature compensation in single or narrow band frequency methods. Inaddition, lower frequencies mean lower signal attenuation (i.e., lesssignal loss) and lower device costs.

The method may further include determining a signal loss value bycomparing the measured magnitude of the received signals of one or morefrequencies to the magnitude of the transmitted signals of the same oneor more frequencies. Where a signal loss value is determined, performingthe temperature compensation may include modifying the signal loss valuebased on the temperature measurement.

The method may include delivering radio frequency signals totransmitting probe 48 and detecting magnitudes of radio frequencysignals reflected by transmitting probe 48. The method may furtherinclude determining the amount of particulate matter trapped in filtermedium 24 based on the detected magnitudes of radio frequency signalsreflected by transmitting probe 48.

The method may include filtering out all received radio frequencysignals except for signals within a predetermined band of frequenciesthat correspond with the frequencies of the signals transmitted bytransmitting probe 48. The method may also include communicating betweencontroller 28 and at least one other component of particulate trapregeneration system 16 via a datalink.

The method may also include activating regeneration device 25 inresponse to a determination that more than a predetermined amount ofparticulate matter is trapped in filter medium 24 to thereby reduce anamount of particulate matter in particulate trap 19. The method mayfurther include activating regeneration device 25 in response to one ormore other trigger conditions.

In some embodiments, the system may be configured to activateregeneration device 25 when more than one trigger condition is met. Forexample, the system may wait until both a particulate loading thresholdand a time-based trigger condition are met before initiating aregeneration event. In other embodiments, the system may be configuredto initiate a regeneration event when the first of multiple possibletrigger conditions is met.

The following is a description of an exemplary system that is configuredto initiate a regeneration event when the first of multiple possibletrigger conditions is met. In such a system, for example, a simple timetrigger (e.g., engine operation time) may provide the utmost reliabilityas no physical characteristics need to be sensed to monitor such atrigger condition. However, depending on other factors, particulateloading in particulate trap 19 may reach a level warranting regenerationat an earlier time than the interval at which the time trigger is set.In order to prevent damage that could result from such a situation, abackpressure or pressure differential trigger may be configured tomonitor for relatively higher levels of particulate loading. Thus, insuch cases where particulate loading has prematurely reached a highlevel, a backpressure or pressure differential trigger may triggerregeneration to remedy excessive particulate loading even before a timetrigger condition is met.

If, for whatever reason, particulate loading has prematurely reached ahigh level, but has not caused a significant increase in backpressure,an actual particulate loading monitoring system may detect the actualamount of particulate matter accumulated in filter medium 24. That is,system 16 may, in some embodiments, be configured to measure the amountof particulates accumulated in particulate trap 19 and initiate aregeneration event if the amount of particulates accumulated inparticulate trap 19 is above a predetermined threshold level.

If, however, neither the backpressure trigger, nor the particulateloading monitoring system successfully detect excessive particulateloading in a given circumstance, then the time trigger may serve toinsure that regeneration occurs at relatively conservative intervals.Further, regeneration may be triggered manually if, for whatever reason,no other trigger conditions are determined to be met, but an operator,owner, service technician, etc. deems that a regeneration may beappropriate based on their own observations.

It will be apparent to those having ordinary skill in the art thatvarious modifications and variations can be made to the disclosed radiofrequency-based particulate loading monitoring system without departingfrom the scope of the invention. Other embodiments of the invention willbe apparent to those having ordinary skill in the art from considerationof the specification and practice of the invention disclosed herein. Itis intended that the specification and examples be considered asexemplary only, with a true scope of the invention being indicated bythe following claims and their equivalents.

1. A particulate trap regeneration system, comprising: a particulatetrap having a filter medium configured to remove one or more types ofparticulate matter from an exhaust flow of an engine; a regenerationdevice configured to reduce an amount of particulate matter in theparticulate trap; and a radio frequency-based particulate loadingmonitoring system configured to determine an amount of particulatematter trapped by the filter medium, the particulate loading monitoringsystem including: at least one radio frequency transmitting probeconfigured to transmit radio frequency signals of predeterminedmagnitude and predetermined frequency toward the filter medium; at leastone radio frequency receiving probe configured to receive and measurethe magnitude of received radio frequency signals that pass through thefilter medium; a temperature sensing device configured to take atemperature measurement indicative of a temperature of the particulatetrap at the time the radio signals are received by the receiving probe;and a controller configured to: determine, based on the measuredmagnitude of received radio frequency signals, a particulate loadingvalue indicative of the amount of particulate matter trapped in thefilter medium; perform a temperature compensation including modifying,based on the temperature measurement, at least one of the following: themeasured magnitude of the received radio frequency signals that passthrough the filter medium; or the particulate loading value; andactivate the regeneration device in response to the particulate loadingmonitoring system detecting more than a predetermined amount ofparticulate matter trapped in the filter medium.
 2. The system of claim1, wherein the controller is configured to modify the measured magnitudeof the received radio frequency signals that pass through the filtermedium.
 3. The system of claim 1, wherein the controller is furtherconfigured to determine a signal loss value by comparing the measuredmagnitude of the received signals of one or more frequencies to themagnitude of the transmitted signals of the same one or morefrequencies, and wherein performing the temperature compensationincludes modifying the signal loss value based on the temperaturemeasurement.
 4. The system of claim 1, wherein the temperaturecompensation involves a function based on the temperature measurementand at least one of the following: the measured magnitude of thereceived radio frequency signals that pass through the filter medium; orthe particulate loading value.
 5. The system of claim 4, wherein thefunction is a third order polynomial.
 6. The system of claim 1, whereinthe temperature compensation involves a look-up table based on thetemperature measurement and at least one of the following: the measuredmagnitude of the received radio frequency signals that pass through thefilter medium; or the particulate loading value.
 7. The system of claim1, wherein the radio frequency signals have a frequency of less thanabout 500 MHz.
 8. The system of claim 1, further including: a radiofrequency synthesizer configured to deliver radio frequency signals tothe radio frequency transmitting probe; wherein the particulate loadingmonitoring system is further configured to detect magnitudes of radiofrequency signals reflected by the radio frequency transmitting probeand determine the amount of particulate matter trapped in the filtermedium based on the detected magnitudes of radio frequency signalsreflected by the radio frequency transmitting probe.
 9. The system ofclaim 1; wherein the system is further configured to filter out allreceived radio frequency signals except for signals within apredetermined band of frequencies that correspond with the frequenciesof the signals transmitted by the radio frequency transmitting probe.10. The system of claim 1, wherein the controller is further configuredto communicate with at least one other component of the particulate trapregeneration system via a datalink.
 11. A method of regenerating aparticulate trap, comprising: determining an amount of particulatematter trapped by a filter medium of a particulate trap configured toremove one or more types of particulate matter from an exhaust flow ofan engine by: transmitting radio frequency signals of predeterminedmagnitude and predetermined frequency toward a filter medium; receivingand measuring the magnitude of received radio frequency signals thatpass through the filter medium; taking a temperature measurementindicative of a temperature of the particulate trap at the time theradio signals are received; determining, based on the measured magnitudeof received radio frequency signals, a particulate loading valueindicative of the amount of particulate matter trapped in the filtermedium; performing a temperature compensation including modifying, basedon the temperature measurement, at least one of the following: themeasured magnitude of the received radio frequency signals that passthrough the filter medium; or the particulate loading value; andactivating a regeneration device, configured to reduce an amount ofparticulate matter in the particulate trap, in response to theparticulate loading monitoring system detecting more than apredetermined amount of particulate matter trapped in the filter medium.12. The method of claim 11, wherein the method includes modifying themeasured magnitude of the received radio frequency signals that passthrough the filter medium.
 13. The method of claim 11, further includingdetermining a signal loss value by comparing the measured magnitude ofthe received signals of one or more frequencies to the magnitude of thetransmitted signals of the same one or more frequencies, and whereinperforming the temperature compensation includes modifying the signalloss value based on the temperature measurement.
 14. The method of claim11, wherein the temperature compensation involves a function based onthe temperature measurement and at least one of the following: themeasured magnitude of the received radio frequency signals that passthrough the filter medium; or the particulate loading value.
 15. Themethod of claim 14, wherein the function is a third order polynomial.16. The method of claim 11, wherein the temperature compensationinvolves a look-up table based on the temperature measurement and atleast one of the following: the measured magnitude of the received radiofrequency signals that pass through the filter medium; or theparticulate loading value.
 17. The method of claim 11, wherein the radiofrequency signals have a frequency of less than about 500 MHz.
 18. Themethod of claim 11, further including: delivering radio frequencysignals to a radio frequency transmitting probe; detecting magnitudes ofradio frequency signals reflected by the radio frequency transmittingprobe; and determining the amount of particulate matter trapped in thefilter medium based on the detected magnitudes of radio frequencysignals reflected by the radio frequency transmitting probe.
 19. Themethod of claim 11, further including filtering out all received radiofrequency signals except for signals within a predetermined band offrequencies that correspond with the frequencies of the signalstransmitted by the radio frequency transmitting probe.
 20. The method ofclaim 11, further including communicating with at least one othercomponent of the particulate trap regeneration system via a datalink.21. A machine comprising: a frame; an exhaust flow producing enginemounted to the frame; and a particulate trap regeneration system,including: a particulate trap having a filter medium configured toremove one or more types of particulate matter from an exhaust flow ofan engine; a regeneration device configured to reduce an amount ofparticulate matter in the particulate trap; and a radio frequency-basedparticulate loading monitoring system configured to determine an amountof particulate matter trapped by the filter medium, the particulateloading monitoring system including: at least one radio frequencytransmitting probe configured to transmit radio frequency signals ofpredetermined magnitude and predetermined frequency toward the filtermedium; at least one radio frequency receiving probe configured toreceive and measure the magnitude of received radio frequency signalsthat pass through the filter medium; a temperature sensing deviceconfigured to take a temperature measurement indicative of a temperatureof the particulate trap at the time the radio signals are received bythe receiving probe; and a controller configured to: determine, based onthe measured magnitude of received radio frequency signals, aparticulate loading value indicative of the amount of particulate mattertrapped in the filter medium; perform a temperature compensationincluding modifying, based on the temperature measurement, at least oneof the following: the measured magnitude of the received radio frequencysignals that pass through the filter medium; or the particulate loadingvalue; and activate the regeneration device in response to theparticulate loading monitoring system detecting more than apredetermined amount of particulate matter trapped in the filter medium.22. The machine of claim 21, wherein the controller is furtherconfigured to determine a signal loss value by comparing the measuredmagnitude of the received signals of one or more frequencies to themagnitude of the transmitted signals of the same one or morefrequencies, and wherein performing the temperature compensationincludes modifying the signal loss value based on the temperaturemeasurement.
 23. The machine of claim 21, wherein the temperaturecompensation involves a third order polynomial function based on thetemperature measurement and at least one of the following: the measuredmagnitude of the received radio frequency signals that pass through thefilter medium; or the particulate loading value.
 24. The machine ofclaim 21, wherein the temperature compensation involves a look-up tablebased on the temperature measurement and at least one of the following:the measured magnitude of the received radio frequency signals that passthrough the filter medium; or the particulate loading value.
 25. Themachine of claim 21, further including: a radio frequency synthesizerconfigured to deliver radio frequency signals to the radio frequencytransmitting probe; wherein the particulate loading monitoring system isfurther configured to detect magnitudes of radio frequency signalsreflected by the radio frequency transmitting probe and determine theamount of particulate matter trapped in the filter medium based on thedetected magnitudes of radio frequency signals reflected by the radiofrequency transmitting probe.
 26. The machine of claim 21, wherein thesystem is further configured to filter out all received radio frequencysignals except for signals within a predetermined band of frequenciesthat correspond with the frequencies of the signals transmitted by theradio frequency transmitting probe.
 27. The machine of claim 21, whereinthe controller is further configured to communicate with at least oneother component of the particulate trap regeneration system via adatalink.